Evaporator or cooking apparatus

ABSTRACT

Evaporator for a product such as a sugar syrup of the type having an inner heating nest. The nest is vertically spaced from the base of the evaporator vessel and is contained in a compartment which communicates with the product inlet and also communicates, by way of a product overflow means, with a lower zone of the vessel. Means put the lower part of the compartment in communication with said lower zone. A device causes the product to pass from said lower zone through the compartment.

United States Patent [72] Inventor Albert Rene Grlndadam Saint-Maur, fiance [21 Appl. No. 836,846

[22] Filed June 26, 1969 [45] Patented Nov. 23, 1971 [73] Assignee S.I.C.E.R. Societe lndustrielle &

Commerciale D'Etudes & De Realisations Attortville, France [32] Priority June 26, 1968 [33] France [54] EVAPORATOR 0R COOKING APPARATUS 25 Claims, 8 Drawing Figs.

[52] US. Cl 127/16, 23/273, 127/15, 127/61, 159/27, 159/45 [51] Int. Cl C13i1/02, C13g l/02, BOld 9/00 [50] FleldolSearch 127/15, 16, 58, 60-64; 23/273, 301; 159/27 F, 45

[56] References Cited UNITED STATES PATENTS 898,147 9/1908 Von Seemen 159/45 1,791,281 2/1931 Morse 159/45 2,326,024 8/1943 Ge0rge.... 159/27 F 3,495,946 2/1970 Hudson 23/273 X FOREIGN PATENTS 703,726 3/1941 Germany 127/61 838,690 3/1939 France 127/15 OTHER REFERENCES Honig, Principles of Sugar Technology" V. 2, pp. 418-20, Elsvier Pub. Co. 1959.

Primary Examiner-Morris O. Wolk Assistant Examiner-D. G. Conlin Attorney-Max Wall ABSTRACT: Evaporator for a product such as a sugar syrup of the type having an inner heating nest. The nest is vertically spaced from the base of the evaporator vessel and is contained in a compartment which communicates with the product inlet and also communicates, by way of a product overflow means, with a lower zone of the vessel. Means put the lower part of the compartment in communication with said lower zone. A device causes the product to pass from said lower zone through the compartment.

PATENTEUMHV 23 1911 3,622,367

sum 2 OF A l i ll];

PMENTEUNUV 23 |97l SHEET 3 OF l EVAPORATOR R COOKING APPARATUS The present invention relates to evaporators and more particularly to cooking apparatuses or boilers in current use in the sugar-making industry and in refineries for crystallizing sugar by concentration of sugar solutions or massecuites.

One of the stages in the production of sugar consists in concentrating a portion of sugar syrup by evaporation until a foot or lower mass of massecuite is obtained, which is a supersaturated solution, seeding this mass of massecuite by a grainfonning operation and then adding in the evaporator the rest of the syrup and concentrating it so as to crystallize it around the germ crystals introduced in the course of the grain-forming operation.

The cooking apparatuses mostly used consist of a vessel or shell at the bottom of which is placed a nest of boiler tubes. The syrup enters by way of the base of the vessel and is heated by heat exchange when it flows in the tubes. Tlie vapors are discharged by way of the top of the apparatus whereas the massecuite accumulates therein. The level of the massecuite therefore rises in the apparatus as the feeding proceeds and of course rises very considerably beyond the top of the nest. When the apparatus is full, the concentrated massecuite is discharged by way of an outlet pipe.

The accumulation of the massecuite above the nest of boiler tubes is unfortunate since it slows down the flow in the nest and this considerably decreases the efficiency of the evaporatron.

Further, preferential flow networks are created which greatly affect the homogeneity of the massecuite. This homogeneity is necessary if sugar crystals of the same size are to be obtained.

In order to increase the efiiciency and decrease the heterogeneity of the massecuite, various solutions have been proposed. One of them comprises accelerating the rate of flow of the massecuite, in particular along the heating surfaces, by provision of special passages or by accelerators, for example mechanical accelerators.

These solutions are costly and give poor results, since the problem of the variable hydrostatic head above the nest has not been eliminated but merely combatted. Moreover, it has been observed that the evaporation efficiency always remains rather low.

The object of the invention is to remedy these drawbacks by means of a cooking apparatus which ensures a rapid and regular flow of the whole of the massecuite with the advantages of evaporation efficiency and homogeneity of the massecuite which results therefrom.

The invention provides an evaporator or cooking apparatus, for a product (syrup), in particular for the sugar-making and refining industries, having an inner heating nest and wherein the nest is raised relative to the base of the evaporator and is contained in a compartment which communicates with the syrup inlet and with a lower zone of the evaporator by way of an overflow and which comprises means for putting its lower part in communication with said lower zone, a device being provided causing the product to pass from said lower zone through the compartment.

Thus, it will be understood that the massecuite no longer exerts on top of the heating nest a pressure which opposes the flow of the product in the latter. It can also be seen that separate paths are provided for the ascending and descending fluxes of the massecuite. It is known that this directed flow greatly encourages the homogeneity of the massecuite since in this way each portion of the massecuite, and not always the same privileged stream lines, receives the heat in turn. Further features and advantages of the invention will be apparent from the ensuring description with reference to the drawings:

In the drawings:

FIGS. 1, 2, 3, and 7 are sectional views of five embodiments of the evaporator of the invention;

FIG. 4 is an outside view, with a part cut away, of another way of achieving the evaporation;

FIG. 6 is a view of an embodiment of the shaft of the impeller and the circulator of the evaporator shown in FIG. 5, and

FIG. 8 shows the evaporating plant comprising three cooking apparatuses according to the invention.

In the various FIGS. identical elements carry the same reference characters. The evaporator or cooking apparatus according to the invention shown in FIG. I is, for example, adapted to concentrate massecuites in the making of sugar.

It comprises a vessel 1 provided with inlet pipes 20, 2b, with a pump P and an outlet pipe 3. Between the tubes 4 of 2 nest 5 of tubes contained in the center compartment 6 of the vessel 1, flows a heating fluid which enters by way of an inlet 7 and is discharged by way of an outlet 8. A condensate discharge pipe 9 and a drain pipe 10 are also provided in the nest 5.

The compartment 6 is spaced from the base II of the vessel 1 owing to the provision of support elements 12 which are fixed to the outer walls, which are composed of insulating material or comprise a double wall or jacket, of the compartment. The elements 12 bear on support elements 13 fixed to the inner walls of the vessel 1. Disposed in the lower peripheral zone 14 which is thus defined in the lower part of the enclosure is, if desired, an agitator or stirrer 15. The volume of this zone 14 represents for example 4060 percent of the total volume of the evaporator. The top of the nest S communicates by way of an overflow with this zone 14 which communicates with the lower part or passage means 16 of the compartment 6 and with the outlet 3. The walls 29 of the nest over and along which the product flows comprise an insulating material or a double wall or jacket.

The lower part of the compartment 6 communicates with the inlet 2a and is provided with a device 17, such as a pump, a circulator, an impeller or Archimedes screw, which causes the product to pass from the lower zone 14 through the nest 5. A spreading device or distributor 18 is located at the base of the nest.

Provided above the nest 5 are sprinkling means 20 which are connected to the inlet 2b. Provided at the top of the enclosure is a conduit 21 for discharging vapors.

The evaporator operates in the following manner:

At the start, the outlet 3 is closed and a small amount of syrup to be concentrated is introduced by way of the inlet 2a. This syrup arrives in the lower compartment 16 of the compartment 6, is raised by the device I7 and sent into the nest 5 in a very regular manner owing to the action of the distributor l The syrup is concentrated in the nest 5 where it loses the vapor which escapes by way of the discharge pipe 21.

The massecuite overflows from the nest and falls by way of the overflow into the lower zone 14 whence it one more passes into the lower part 16 of the compartment 6 and is recycled to the nest 5.

Thus the massecuite is raised until the level of the latter in the lower zone reaches substantially that of the top of the nest. At this stage, it is preferable to feed fresh syrup by means of the sprinkling means connected to the inlet 2b.

In the evaporator shown in FIG. 2, the nest 5 is located at the center of the compartment 6 with the periphery of which it communicates by way of an overflow. This constitutes a small inner boiler which ensures a rapid production of a foot or base mass of massecuite while employing only a small amount of syrup.

The passage for putting the lower zone 14 in communication with the lower part 16 of the compartment is a pipe 28.

This evaporator is moreover equipped with jackets 23 for heating the lower zone 14 and the compartment 6 and with heating elements 23, for example steam injectors, for heating the lower zone.

Further, provided at the base of the nest 5 are baffles 24 and provided above the nest are screens 25, for example plates having apertures.

This evaporator operates in a manner similar to that of the evaporator shown in FIG. 1 except that:

a. There is a first overflow of massecuite from the nest 5 into the compartment 6. When the latter is full, there is a second overflow of the massecuite from the compartment 6 into the lower zone 14, screens 25 serving to separate these two fluxes of massecuite and baffles 24 serving to send the flux of massecuite coming from the overflow of the compartment 16 preferably into the peripheral tubes rather than into the center tubes of the nest.

b. a portion of the massecuite which accumulates in the lower zone 14 is recycled to the compartment 6 (as in the evaporator shown in FIG. 1) by flowing in the pipe 28 specially provided for this purpose.

In FIG. 3 the nest 5 is located at the periphery of the compartment 6 with the center of which it communicates by way of an overflow. It communicates by way of its periphery with the lower zone 14.

Further, a circulator 26 is passage through the nest 5 of flown into the compartment 6.

It will also be observed that the lower part 16 of the compartment and the outlet are offcenter relative to the axis of the evaporator so as to leave a free space for a shaft of the circulator or of a stirring device.

Thus, in FIG. 5 the device 17 for causing the product to pass from the lower zone through the compartment and the circulator 26 are mounted on a common axial shaft 29 extending through the vessel wall.

The device 17 and the circulator 26 can also be mounted on two shafts 29a, 29b which are coaxial and driven respectively by two motors 30a, 3012 as shown in FIG, 6, so that it is possible to drive them at different speeds.

It will be observed that in the embodiment shown in FIG. 5, the shaft 29 extends into the evaporator through the base of the latter. This is advantageous since this avoids the necessity of providing bearings inside the evaporator.

In FIG. 7 the shaft 32 of the device for causing the product to pass from the lower zone through the compartment extends into the evaporator through the base of the latter and the shaft 31 of the circulator extends into the evaporator through the top of the latter.

Further, the lower zone 14 of the evaporator is separated from the chamber 34 above the nest. The latter however communicates with the lower zone 14 by way of an overflow and by way of passage means in the form of a pipe 32 extending outside the vessel of the evaporator and provided with a valve 33.

In FIG, 4 the nest consists of a main nest 5a and an auxiliary nest 5b which are independent. These nests have their own respective compartments 6a, 6b. This embodiment of the evaporator according to the invention facilitates the obtainment of a foot or base mass of massecuite with a small amount of syrup.

It is possible, as shown in FIG. 8, to provide a plant for concentrating syrup comprising a plurality, for example three, evaporators according to the invention connected in series relation.

This plant comprises a steam supply pipe 27 common to the three evaporators A, B, C, the outlet pipe 3A being connected to the inlet pipe 28, and the outlet pipe 38 to the inlet pipe 2C through pumps PA and PB respectively. The massecuite is progressively concentrated as it passes from the evaporator A to the evaporator B, then from the latter to the evaporator C.

The scope of the invention is not intended to be limited to the shape or the arrangement of the nest which can be of the type having tubes or plates, it being inclined, horizontal or vertical and operating continuously or discontinuously.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. An evaporator for a product, in particular for sugar making and refineries, said evaporator comprising a vessel having a base, a product inlet communicating with the interior of said vessel, a compartment within said vessel and having a lower wall, an inner heating nest within said compartment, said nest having tubes for receiving an upward flow of the product, said tubes having lower inlets in spaced relation to said lower wall to allow the product access to said tube inlets, said compartprovided for accelerating the the massecuite which has overment being vertically spaced from said base of said vessel, a lower zone defined between said lower wall of said compartment and said vessel, said lower zone having a lower part, a product outlet communicating with the interior of said vessel in said lower part of said lower zone, said compartment having product overflow means in an upper part of said vessel and communicating with said product inlet, first passage means putting said overflow means in communication with said lower zone, second passage means for putting a lower part of said compartment adjacent said lower wall of said compartment in communication with said lower part of said lower zone, and a device for causing said product to flow from said lower part of said lower zone upwardly through said second passage means, said lower part of said compartment and thence through said tubes and past said overflow means.

2. An evaporator as claimed in claim 1, wherein said device for causing said product to pass from said lower zone through said compartment is a pump.

3. An evaporator as claimed in claim 1, wherein said device for causing said product to pass from said lower zone through said compartment is an impeller.

4. An evaporator as claimed in claim 1, wherein said device for causing said product to pass from said lower zone through said compartment is an Archimedes screw operative to urge the product downwardly.

5. An evaporator as claimed in claim I, wherein said compartment is located at the center of said vessel and said lower zone at the periphery.

6. An evaporator as claimed kling means connected to said said nest.

7. An evaporator as claimed in claim 1, comprising a stirrer located in said lower zone.

8. An evaporator as claimed in claim I, comprising a heating device located in said lower zone.

9. An evaporator as claimed in claim 1, wherein said nest comprises a main nest and an auxiliary nest which are independent from each other and have their own respective compartments.

10. An evaporator as claimed in claim 1, wherein said outlet is offset relative to the axis of said vessel so as to leave a free space in the base of the vessel in which free space of the base is disposed a shaft driving a product driving means.

11. An evaporator as claimed in claim 1, wherein said compartment extends completely across the cross section of said vessel and defines a chamber in an upper part of the vessel, said means putting said overflow means in communication with said lower zone comprising a pipe which extends outside said vessel and has a valve, said nest being annular and defining a center free space communicating with said lower part of said compartment, means being provided for preventing upward flow of the product in said center free space.

12. An evaporator as claimed in claim 1, wherein said nest is located at the periphery of said compartment and includes product overflow means, said nest communicating with the center of said compartment by way of said product overflow means of said nest, said evaporator further comprising a circulator for accelerating the recycling of said product from the lower part of the compartment through the nest.

13. An evaporator as claimed in claim 12, wherein said overflow means of said nest comprises a wall along which said product overflows, said wall including an insulating material.

14. An evaporator as claimed in claim 12, wherein provide overflow means of said nest comprises a wall along which said product overflows, said wall including a jacket.

15. An evaporator as claimed in claim 1, wherein said device for causing the product to pass from said lower zone through said compartment is a circulator.

16. An evaporator as claimed in 15, 26, wherein said nest has peripheral product overflow means and is located at the center of said compartment and defines an annular space with said compartment, said nest communicating with the periphery of said compartment by way of said product overin claim 1, comprising sprinproduct inlet and located above flow means of said nest said compartment defining an annular gap with said vessel which gap constitutes said first passage means and said compartment having product overflow means on the periphery of said compartment.

17. An evaporator as claimed in claim 16, wherein said overflow means of said nest comprises a wall along which said product overflows, said wall including an insulating material.

18. An evaporator as claimed in claim 16, wherein said overflow means of said nest comprises a wall along which said product overflows, said wall including a jacket.

19. An evaporator for a product, in particular for sugar making and refineries, said evaporator comprising a vessel having a base, a product inlet and a product outlet communicating with the interior of said vessel, a compartment within said vessel and having a lower part, an inner heating nest within said compartment, said compartment being vertically spaced from said base of said vessel, a lower zone defined between said compartment and said vessel, said compartment having product overflows means and communicating with said product inlet and communicating with sand lower zone by way of said overflow means, means for putting the lower part of said compartment in communication with said lower zone, a device for causing said product to pass from said lower zone through said compartment, said nest being located at the periphery of said compartment and including product overflow means, said nest communicating with the center of said compartment by way of said product overflow means of said nest, and a circulator for accelerating the recycling of said product from the lower part of said compartment through said nest, said device for causing said product to pass from said lower zone through said compartment and said circulator being mounted on a common drive shaft.

20. A evaporator as claimed in claim 19, wherein said shaft extends into said vessel through the base of said vessel.

21. An evaporator for a product, in particular for sugar making and refineries, said evaporator comprising a vessel having a base, a product inlet and a product outlet communicating with the interior of said vessel, a compartment within said vessel and having a lower part, an inner heating nest within said compartment, said compartment being vertically spaced from said base of said vessel, a lower zone defined between said compartment and said vessel, said compartment having product overflow means and communicating with said product inlet and communicating with said lower zone by way of said overflow means, mans for putting the lower part of said compartment in communication with said lower zone, a device for causing said product to pass from said lower zone through said compartment, said nest being located at the periphery of said compartment and including product overflow means, said nest communicating with the center of said compartment by way of said product overflow means of said nest, and a circulator for accelerating the recycling of said product from the lower part of said compartment through said nest, said device for causing said product to pass from said lower zone through said compartment and said circulator being mounted on two coaxial shafts which are respectively driven by two motors.

22. An evaporator as claimed in claim 21, wherein aid shafts extend into said vessel through the base of said vessel.

23. An evaporator for a product, in particular for sugar making and refineries, said evaporator comprising a vessel having a base, a product inlet and a product outlet communicating with the interior of said vessel, a compartment within said vessel and having a lower part, an inner heating nest within said compartment, said compartment being vertically spaced from said base of said vessel, a lower zone defined between said compartment and said lower zone defined between said compartment and said vessel, said compartment having product overflow means and communicating with said product inlet and communicating with said lower zone by way of said overflow means, means for putting the lower part of said compartment in communication with said lower zone, a

device for causing said product to pass from said lower zone through said compartment, said nest being located at the periphery of said compartment and including product overflow means, said nest communicating with the center of said compartment by way of said product overflow means of said nest, and a circulator and a shaft connected to the circulator for rotating the circulator so as to accelerate the recycling of said product from the lower part of said compartment through said nest, said shaft of said device for causing said product to pass from said lower zone through said compartment having product stirring means and a shaft which is connected to the stirring means for rotating said stirring means and extends into said vessel through the base of said vessel and said shaft connected to said circulator extending into said vessel trough the top of said vessel.

24. An evaporating installation for a product, in particular for sugar making and refineries, comprising a plurality of evaporators; each evaporator comprising a vessel having a base, a product inlet communicating with the interior of said vessel, a compartment within said vessel and having a lower wall, an inner heating nest within said compartment, said nest having tubes for receiving an upward flow of the product, said tubes having lower inlets in spaced relation to said lower wall to allow the product access to said tube inlets, said compartment being vertically spaced from said base of said vessel, a lower zone defined between said lower wall of said compartment and said vessel, said lower zone having a lower part, a product outlet communicating with the interior of said vessel in said lower part of said lower zone, said compartment having product overflow means in a upper part of said vessel and communicating with said product inlet, first passage means putting said overflow means in communication with said lower zone, second passage means for putting a lower part of said compartment adjacent said lower wall of said compartment in communication with said lower part of said lower zone, and a device for causing said product to flow from said lower part of said lower zone upwardly through said second passage means, said lower part of said compartment and thence through said tubes and past said overflow means; said evaporators being operatively connected in series relation, the product outlet of one evaporator being connected to the product inlet of a following evaporator.

25. An evaporator for a product in particular of sugar making and refineries, said evaporator comprising a vessel having a base, product inlet means communicating with the interior of said vessel, a compartment within said vessel and having a lower wall, an inner heating nest of tubes within the interior of said compartment, said tubes having lower product inlets in spaced relation to said lower wall to allow the product access to said tube inlets, said compartment having product overflow means located in an upper half of the inside of the vessel and communicating with said product inlet means, said lower wall of said compartment defining with said base of said vessel a lower zone of the interior of the vessel which has a volume of 40-60 percent of the total volume of the interior of said vessel for receiving the product, first passage means putting said overflow means in communication with said lower zone for allowing the product from said overflow means to reach said lower zone, said lower zone having a lower part, product outlet means in said vessel in said lower part of said lower zone,

A second passage means depending from said lower wall of said compartment and extending to said lower part of said lower zone whereby a lower part of the interior of said compartment adjacent said lower wall communicates with said lower part of said lower zone, and mechanical means within said second passage means for causing the product to flow from said lower part of said lower zone upwardly through said second passage means, through said tubes and beyond said overflow means.

* i i i 

2. An evaporator as claimed in claim 1, wherein said device for causing said product to pass from said lower zone through said compartment is a pump.
 3. An evaporator as claimed in claim 1, wherein said device for causing said product to pass from said lower zone through said compartment is an impeller.
 4. An evaporator as claimed in claim 1, wherein said device for causing said product to pass from said lower zone through said compartment is an archimedes screw operative to urge the product downwardly.
 5. An evaporator as claimed in claim 1, wherein said compartment is located at the center of said vessel and said lower zone at the periphery.
 6. An evaporator as claimed in claim 1, comprising sprinkling means connected to said product inlet and located above said nest.
 7. An evaporator as claimed in claim 1, comprising a stirrer located in said lower zone.
 8. An evaporator as claimed in claim 1, comprising a heating device located in said lower zone.
 9. An evaporator as claimed in claim 1, wherein said nest comprises a main nest and an auxiliary nest which are independent from each other and have their own respective compartments.
 10. An evaporator as claimed in claim 1, wherein said outlet is offset relative to the axis of said vessel so as to leave a free space in the base of the vessel in which free space of the base is disposed a shaft driving a product driving means.
 11. An evaporator as claimed in claim 1, wherein said compartment extends completely aCross the cross-section of said vessel and defines a chamber in an upper part of the vessel, said means putting said overflow means in communication with said lower zone comprising a pipe which extends outside said vessel and has a valve, said nest being annular and defining a center free space communicating with said lower part of said compartment, means being provided for preventing upward flow of the product in said center free space.
 12. An evaporator as claimed in claim 1, wherein said nest is located at the periphery of said compartment and includes product overflow means, said nest communicating with the center of said compartment by way of said product overflow means of said nest, said evaporator further comprising a circulator for accelerating the recycling of said product from the lower part of the compartment through the nest.
 13. An evaporator as claimed in claim 12, wherein said overflow means of said nest comprises a wall along which said product overflows, said wall including an insulating material.
 14. An evaporator as claimed in claim 12, wherein said overflow means of said nest comprises a wall along which said product overflows, said wall including a jacket.
 15. An evaporator as claimed in claim 1, wherein said device for causing the product to pass from said lower zone through said compartment is a circulator.
 16. An evaporator as claimed in claim 15, wherein said nest has peripheral product overflow means and is located at the center of said compartment and defines an annular space with said compartment, said nest communicating with the periphery of said compartment by way of said product overflow means of said nest, said compartment defining an annular gap with said vessel which gap constitutes said first passage means and said compartment having product overflow means on the periphery of said compartment.
 17. An evaporator as claimed in claim 16, wherein said overflow means of said nest comprises a wall along which said product overflows, said wall including an insulating material.
 18. An evaporator as claimed in claim 16, wherein said overflow means of said nest comprises a wall along which said product overflows, said wall including a jacket.
 19. An evaporator for a product, in particular for sugar making and refineries, said evaporator comprising a vessel having a base, a product inlet and a product outlet communicating with the interior of said vessel, a compartment within said vessel and having a lower part, an inner heating nest within said compartment, said compartment being vertically spaced from said base of said vessel, a lower zone defined between said compartment and said vessel, said compartment having product overflow means and communicating with said product inlet and communicating with said lower zone by way of said overflow means, means for putting the lower part of said compartment in communication with said lower zone, a device for causing said product to pass from said lower zone through said compartment, said nest being located at the periphery of said compartment and including product overflow means, said nest communicating with the center of said compartment by way of said product overflow means of said nest, and a circulator for accelerating the recycling of said product from the lower part of said compartment through said nest, said device for causing said product to pass from said lower zone through said compartment and said circulator being mounted on a common drive shaft.
 20. An evaporator as claimed in claim 19, wherein said shaft extends into said vessel through the base of said vessel.
 21. An evaporator for a product, in particular for sugar making and refineries, said evaporator comprising a vessel having a base, a product inlet and a product outlet communicating with the interior of said vessel, a compartment within said vessel and having a lower part, an inner heating nest within said compartment, said compartment being vertically spaced from said base of said vessel, a lower zone defineD between said compartment and said vessel, said compartment having product overflow means and communicating with said product inlet and communicating with said lower zone by way of said overflow means, means for putting the lower part of said compartment in communication with said lower zone, a device for causing said product to pass from said lower zone through said compartment, said nest being located at the periphery of said compartment and including product overflow means, said nest communicating with the center of said compartment by way of said product overflow means of said nest, and a circulator for accelerating the recycling of said product from the lower part of said compartment through said nest, said device for causing said product to pass from said lower zone through said compartment and said circulator being mounted on two coaxial shafts which are respectively driven by two motors.
 22. An evaporator as claimed in claim 21, wherein said shafts extend into said vessel through the base of said vessel.
 23. An evaporator for a product, in particular for sugar making and refineries, said evaporator comprising a vessel having a base, a product inlet and a product outlet communicating with the interior of said vessel, a compartment within said vessel and having a lower part, an inner heating nest within said compartment, said compartment being vertically spaced from said base of said vessel, a lower zone defined between said compartment and said vessel, said compartment having product overflow means and communicating with said product inlet and communicating with said lower zone by way of said overflow means, means for putting the lower part of said compartment in communication with said lower zone, a device for causing said product to pass from said lower zone through said compartment, said nest being located at the periphery of said compartment and including product overflow means, said nest communicating with the center of said compartment by way of said product overflow means of said nest, and a circulator and a shaft connected to the circulator for rotating the circulator so as to accelerate the recycling of said product from the lower part of said compartment through said nest, said shaft of said device for causing said product to pass from said lower zone through said compartment having product stirring means and a shaft which is connected to the stirring means for rotating said stirring means and extends into said vessel through the base of said vessel and said shaft connected to said circulator extending into said vessel trough the top of said vessel.
 24. An evaporating installation for a product, in particular for sugar making and refineries, comprising a plurality of evaporators; each evaporator comprising a vessel having a base, a product inlet communicating with the interior of said vessel, a compartment within said vessel and having a lower wall, an inner heating nest within said compartment, said nest having tubes for receiving an upward flow of the product, said tubes having lower inlets in spaced relation to said lower wall to allow the product access to said tube inlets, said compartment being vertically spaced from said base of said vessel, a lower zone defined between said lower wall of said compartment and said vessel, said lower zone having a lower part, a product outlet communicating with the interior of said vessel in said lower part of said lower zone, said compartment having product overflow means in an upper part of said vessel and communicating with said product inlet, first passage means putting said overflow means in communication with said lower zone, second passage means for putting a lower part of said compartment adjacent said lower wall of said compartment in communication with said lower part of said lower zone, and a device for causing said product to flow from said lower part of said lower zone upwardly through said second passage means, said lower part of said compartment and thence through said tubes and past said overfLow means; said evaporators being operatively connected in series relation, the product outlet of one evaporator being connected to the product inlet of a following evaporator.
 25. An evaporator for a product, in particular for sugar making and refineries, said evaporator comprising a vessel having a base, product inlet means communicating with the interior of said vessel, a compartment within said vessel and having a lower wall, an inner heating nest of tubes within the interior of said compartment, said tubes having lower product inlets in spaced relation to said lower wall to allow the product access to said tube inlets, said compartment having product overflow means located in an upper half of the inside of the vessel and communicating with said product inlet means, said lower wall of said compartment defining with said base of said vessel a lower zone of the interior of the vessel which has a volume of 40 - 60 percent of the total volume of the interior of said vessel for receiving the product, first passage means putting said overflow means in communication with said lower zone for allowing the product from said overflow means to reach said lower zone, said lower zone having a lower part, product outlet means in said vessel in said lower part of said lower zone, second passage means depending from said lower wall of said compartment and extending to said lower part of said lower zone whereby a lower part of the interior of said compartment adjacent said lower wall communicates with said lower part of said lower zone, and mechanical means within said second passage means for causing the product to flow from said lower part of said lower zone upwardly through said second passage means, through said tubes and beyond said overflow means. 